No prior screening will be performed for the American control subjects, other than that they state they are healthy and have no acute or chronic medical problems. For the Kenyan adult control subjects, they will also be queried about their general overall perceived health and will have no known acute or chronic illnesses. A FSB sample will be obtained from the Kenyan control subjects and tested for anti-bodies to MSP142, a blood smear for malaria, and hemoglobin concentration by Hemacue test. If the hemoglobin concentration is <10 gm/dL, the subject will not be asked to donate blood and will be referred to the appropriate health care deliverers to receive appropriate treatment (oral iron supplements).